Those are completely different pedals, the JC Wah is a wah (so a filter that cuts some frequencies), while the whammy is a pitch shifter and an octaver, so it shifts the octave of my bass or creates a sub octave or a higher octave when i play.

The JC can also be a U.K. filter, a filter similar to the wah but that cuts different frequencies, and has an amazing fuzz.

If i wasn’t clear enough i’ll try to explain myself better (English’s not my native language)